Whether or not sampling has artistic merit and if Kanye is a genius are two different questions.
1. Sampling has artistic merit if done creatively. Producers such as MC Hammer and Puff Daddy got a bad rap (no pun intended) for sampling easy to recognize 80s hit singles. Even Dr Dre got flack during his G-Funk reign for excessive sampling of Parliament/Funkadelic.
Producers like Q-Tip, DJ Premiere, Pete Rock, RZA, etc. get a pass for finding rare, obscure songs to sample. Songs that would otherwise be forgotten.
2. Kanye was really good at producing music in the early 2000s. From The Blueprint to College Dropout he had his own unique sound and style that could only be matched by Just Blaze and Pharell. But that doesn't make him a genius. It just means he was really good at what he did. He had a staff of people to handle the marketing and promotion and he did his job. I'd say he was in the right place at the right time. I haven't heard his recent material (or his new album) so I can't really comment on The Life of Pablo.
There's hundreds of producers right now on soundcloud that make dope beats but for whatever reason don't have the financial backing to produce an album that would make a dent in todays market. Producers need a major label to pay for sample clearances and connections to a well known artist. Thats how Kanye got his break.